The goal of our proposed research is to understand the molecular mechanisms underlying thermotaxis in the fruitfly, Drosophila melanogaster. Thermotaxis, which is the movement towards a preferred temperature, has been studied in a wide range of vertebrate and invertebrate organisms. However, only a few of the genes and proteins required for temperature discrimination are known. There are two rationales for the proposed research. First, thermotaxis in insects has potential medical relevance, as the host-seeking behaviors of disease spreading vectors, such as the malaria-spreading insect, Anopheles gambiae, appear to involve temperature sensation. Thus, identification of the proteins essential for this behavior may lead to approaches to interfere with it. Drosophila homologs of TRP channels, which are thermosensors in mammals, also function in thermotaxis. Since several thermoTRPs in mammals are also regulated by aversive chemicals, we propose that Drosophila thermoTRPs may be targets for insect repellents. The discovery of the molecular targets for repellents has medical implications, given that mosquito-borne disease is a worldwide health problem. Second, the observations that TRPs are themosensors in flies and mammals raise the possibility that other proteins that function in thermosensation may be shared. Thus, identification of genes and proteins that function in Drosophila thermotaxis may provide new insights into mammalian thermosensation. To characterize thermotaxis and thermoTRPs, we propose to use a multidisciplinary approach, using a combination of genetics, biochemistry, cell biology, molecular biology and electrophysiology. The specific aims of the current proposal are to: 1) test the hypothesis that a TRP channel (Painless) functions in thermotaxis in adult flies, 2) test the hypothesis that thermoTRPs are targets for insect repellents, 3) test the hypothesis that the TRPV channels (Nanchung and Inactive) operate in combination for larval thermotaxis, and 4) test the hypothesis that rhodopsins function in a thermotaxis signaling pathway. This last aim is concerned with testing the proposal that rhodopsins are direct thermosensors, which may account for the long-known phenomenon that dark-noise and spontaneous activation of rhodopsin is temperature sensitive. A long-term goal of the proposed research is to apply the insights on Drosophila thermoTRPs to identify improved insect repellents and to test the efficacies of drugs that inhibit thermally-driven thermotaxis behaviors that could be applied to medically important Diptera. PUBLIC HEALTH RELEVANCE: The proposed research is concerned with identifying the genes and proteins that are important for thermotaxis and the responses to insect repellents, in the fruitfly. A long-term goal of the proposed research is to apply the insights on fruitfly to identify improved insect repellents and to test the efficacies of drugs that inhibit thermally-driven thermotaxis behaviors that could be applied to medically important insects, such as those that spread malaria and West Nile Virus.